Evaluation of test methods to measure cold tolerance in cotton

Profitable cotton (Gossypium hirsutum L.) production on the Southern High Plains of Texas is dependent upon an interaction of many environmental and physiological factors that vary from year to year. The first goal in cotton production is the establishment of a uniform and vigorous healthy stand of seedlings in the field. The establishment of an ideal stand of cotton seedlings on the Southern High Plains, where planting typically begins in May, is often impaired by suboptimum environmental conditions. Environmental conditions during planting are characterized by cool nights due to the areas high elevation, low relative humidity, and lingering cold fronts. These environmental conditions allow for temperatures to fall below critical levels for optimum seedling germination and establishment such that seedlings may experience chilling injury. Producers, however, often must plant in these suboptimal and potentially detrimental conditions because of the area's short growing season. This allows the crop to mature before temperatures drop below critical levels for crop maturation in the fall which would compromise lint yield and quality.

Low temperatures play a critical role in seedling germination, establishment, growth and development of many tropical and subtropical crops such as cotton which are chilling sensitive. Crops that are chillng sensitive are injured or killed by low temperatures that are well above freezing. Chilling injury in cotton is characterized by low germination, low vigor seedlings, aborted radicle root tips, and delayed crop maturation. The optimum temperature for cotton seedling germination and establishment is between 30-35° C. Physiological zero for cotton is considered around 15° C, although chilling damage has been reported as high as 20° C.